1. Field of the Invention
The present invention relates to a method for etching an organic film, a method for fabricating a semiconductor device and a pattern formation method.
2. Description of the Related Art
For the purpose of increasing the operation speed and lowering the consumption power of semiconductor devices, decrease of the dielectric constant of an interlayer insulating film included in a multi-level interconnect structure is recently regarded as significant. In particular, an organic film with a small dielectric constant can be easily formed by spin coating and curing, and hence is regarded as a very promising interlayer insulating film of the next generation. A well known example of the organic film with a small dielectric constant is an organic film including an aromatic polymer as a base.
In order to fabricate a device with a refined design rule of a gate length of 0.18 xcexcm or less, a fine interconnect processing technique of approximately 0.25-xcexcm or less is necessary, and the design rule is considered to be more and more refined in the future. An organic film is generally patterned by plasma etching, but a fine pattern of 0.25 xcexcm or less is very difficult to form from an organic film.
Known examples of the plasma etching employed for an organic film are a process using an etching gas including a N2 gas and a H2 gas as principal constituents (reported by M. Fukusawa, T. Hasegawa, S. Hirano and S. Kadomura in xe2x80x9cProc. Symp. Dry Processxe2x80x9d, p. 175 (1998)) and a process using an etching gas including a NH3 gas as a principal constituent (reported by M. Fukusawa, T. Tatsumi, T. Hasegawa, S. Hirano, K. Miyata and S. Kadomura in xe2x80x9cProc. Symp. Dry Processxe2x80x9d, p. 221 (1999).
One of conventional etching methods will now be described as Conventional Example 1 referring to the result obtained by etching an organic film with a magnetic neutral loop discharge (NLD) plasma etching system manufactured by ULVAC JAPAN, Ltd. (xe2x80x9cSiO2 Etching in magnetic neutral loop discharge plasmaxe2x80x9d, W. Chen, M. Itoh, T. Hayashi and T. Uchida, J. Vac. Sci. Technol., A16 (1998) 1594).
In Conventional Example 1, an organic film is etched by using an etching gas including a N2 gas and a H2 gas as principal constituents. The present inventors have carried out the etching process of Conventional Example 1 under the following conditions:
Plasma etching system: NLD plasma etching system
Volume flow ratio per minute in standard condition of etching gas:
N2:H2=50 ml:50 ml
Antenna power: 1000 W (13.56 MHz)
Bias power: 200 W (2 MHz)
Pressure: 0.4 Pa
Substrate cooling temperature: 0xc2x0 C.
Etching time: 180 seconds
FIGS. 16A through 16D are cross-sectional SEM photographs of holes formed under the aforementioned etching conditions in organic films, and the holes of FIGS. 16A through 16D have diameters of 0.16 xcexcm, 0.18 xcexcm, 0.24 xcexcm and 0.40 xcexcm, respectively. In FIGS. 16A through 16D, a reference numeral 101 denotes a silicon substrate, a reference numeral 102 denotes an organic film to be etched, and a reference numeral 103 denotes a mask pattern of a silicon oxide film used as a mask in etching the organic film 102. The organic film 102 has a thickness of approximately 1.02 xcexcm, and the mask pattern 103 has a thickness of approximately 240 nm.
In a multi-level interconnect structure of a semiconductor device, a lower interconnect, an interlayer insulating film and an upper interconnect are successively stacked, and the lower interconnect and the upper interconnect are connected to each other through a pillar-shaped plug formed in the interlayer insulating film. Also, single damascene and dual damascene methods have recently been developed. In the single damascene method, a via hole or an interconnect groove is formed in an interlayer insulating film and is subsequently filled with a metal material, so as to form a connection plug or a metal interconnect. In the dual damascene method, a via hole and an interconnect groove are formed in an interlayer insulating film and are subsequently filled with a metal material, so as to simultaneously form a connection plug and a metal interconnect.
Now, the conventional single damascene method will be described as Conventional Example 2 with reference to FIGS. 17A through 17E and 18A through 18D.
First, as is shown in FIG. 17A, a laminated metal interconnect consisting of a first barrier metal layer 212, a metal film 213 and a second barrier metal layer 214 is formed on a semiconductor substrate 211. Then, as is shown in FIG. 17B, an organic film 215 is formed on the metal interconnect, and thereafter, a silicon oxide film 216 is formed on the organic film 215 as is shown in FIG. 17C.
Then, a resist pattern 217 is formed on the silicon oxide film 216 by a known lithography technique as is shown in FIG. 17D. Thereafter, the silicon oxide film 216 is subjected to plasma etching (dry etching) using the resist pattern 217 as a mask, so as to form a mask pattern 216A from the silicon oxide film 216 as is shown in FIG. 17E.
Next, the organic film 215 is etched by the method for Conventional Example 1 by using the mask pattern 216A, so as to form a recess 218 for a via hole or an interconnect groove in the organic film 215 as is shown in FIG. 18A. Since the resist pattern 217 is formed from an organic compound, it is removed during the etching of the organic film 215.
Subsequently, a third barrier metal layer 219 of TiN or TaN with a small thickness is formed on the wall of the recess 218 by sputtering as is shown in FIG. 18B.
Then, the recess 218 is filled with a conducting film 222 by chemical vapor deposition (CVD) or plating as is shown in FIG. 18C, and a portion of the conducting film 222 formed outside the recess 218 is removed by chemical mechanical polishing (CMP). Thus, a connection plug or metal interconnect 223 is formed as is shown in FIG. 18D.
The conventional dual damascene method will now be described as Conventional Example 3 with reference to FIGS. 19A through 19D, 20A through 20C and 21A through 21C.
First, as is shown in FIG. 19A, a lower laminated metal interconnect consisting of a first barrier metal layer 232, a metal film 233 and a second barrier metal layer 234 is formed on a semiconductor substrate 231. Then, a first organic film 235 is formed on the lower metal interconnect as is shown in FIG. 19B, and a first silicon oxide film 236 is formed on the first organic film 235 as is shown in FIG. 19C.
Next, a first resist pattern 237 having an opening for a via hole is formed on the first silicon oxide film 236 by a known lithography technique as is shown in FIG. 19D. Then, the first silicon oxide film 236 is subjected to plasma etching (dry etching) by using the first resist pattern 237 as a mask, so as to form a first mask pattern 236A from the first silicon oxide film 236 and remove the first resist pattern 237 as is shown in FIG. 20A. Thereafter, a top face of the first mask pattern 236A is cleaned so as not to damage the first organic film 235.
Then, as is shown in FIG. 20B, a second organic film 238 is formed on the first mask pattern 236A, and a second silicon oxide film 239 is formed on the second organic film 238.
Next, as is shown in FIG. 20C, a second resist pattern 240 with an opening for an interconnect groove is formed on the second silicon oxide film 239. Thereafter, the second silicon oxide film 239 is etched by using the second resist pattern 240 as a mask, so as to form a second mask pattern 239A from the second silicon oxide film 239 as is shown in FIG. 21A.
Subsequently, the second organic film 238 and the first organic film 235 are etched by the method for Conventional Example 1, so as to form an interconnect groove 241 by transferring the second mask pattern 239A onto the second organic film 238 and form a via hole 242 by transferring the first mask pattern 236A onto the first organic film 235 as is shown in FIG. 21B. FIG. 21B shows a state where the via hole 242 is being formed in the first organic film 235, and as shown in this drawing, a deposition including a reaction product generated through the reaction between the etching gas and the first organic film 235 and silicon released from the first mask pattern 236A is adhered onto the wall of the via hole 242, resulting in forming a barrier wall 243 from the deposition.
Next, the second organic film 238 and the first organic film 235 are continuously etched by the method for Conventional Example 1, so as to completely form the via hole 242 in the first organic film 235 as is shown in FIG. 21C. Thereafter, the second barrier metal layer 234 is over-etched so as to completely remove the first organic film 235 remaining on the second barrier metal layer 234. The second resist pattern 240 is completely removed through the etching and the over-etching.
Then, although not shown in the drawings, a third barrier metal layer with a small thickness is formed on the walls of the interconnect groove 241 and the via hole 242 in the same manner as in Conventional Example 2, and the interconnect groove 241 and the via hole 242 are filled with a conducting film. Thereafter, a portion of the conducting film formed outside the connection groove 241 is removed by the CMP. Thus, a connection plug and an upper metal interconnect are formed.
As methods of forming a mask pattern through dry development (plasma etching) of an organic film, a top surface imaging (TSI) process, a three-layer resist process and the like are known.
In the top surface imaging process, a surface of an organic film resulting from pattern exposure is subjected to silylation, so as to selectively form a silylated layer on an exposed or unexposed portion of the organic film. Then, the organic film is subjected to dry development (plasma etching) using the silylated layer as a mask, so as to form a resist pattern.
Now, a pattern formation method using dry development (top surface imaging process) will be described as Conventional Example 4 with reference to FIGS. 22A through 22D.
First, as is shown in FIG. 22A, an organic film 252 is formed on a semiconductor substrate 251, and then a silylation target layer 253 is formed on the organic film 252.
Next, as is shown in FIG. 22B, the silylation target layer 253 is irradiated with exposing light 254 through a photomask 255 for selectively allowing the light to pass, so as to selectively form a decomposed layer 256 in the silylation target layer 253.
Then, as is shown in FIG. 22C, with the substrate temperature increased, a gaseous silylation reagent 257 is supplied onto the silylation target layer 253, so as to selectively silylate a non-decomposed portion (a portion excluding the decomposed layer 256) of the silylation target layer 253. Thus, a silylated layer 258 is formed. Instead of silylating the non-decomposed portion, the decomposed layer 256 may be silylated to form the silylated layer 258.
Next, the organic film 252 is etched by the method for Conventional Example 1 by using the silylated layer 258 as a mask, so as to form an organic film pattern (mask pattern) 252A from the organic film 252 as is shown in FIG. 22D.
Another pattern formation method using dry development (three-layer resist process) will now be described as Conventional Example 5.
First, an organic film and a silicon oxide film are successively formed on a semiconductor substrate, and a thin resist pattern is then formed on the silicon oxide film.
Then, the silicon oxide film is subjected to plasma etching by using the resist pattern as a mask, so as to form a mask pattern by transferring the resist pattern onto the silicon oxide film. Thereafter, the organic film is subjected to dry development by using the mask pattern, so as to form a fine organic film pattern with a high aspect ratio from the organic film.
Next, by using a two-layer mask pattern consisting of the mask pattern and the organic film pattern, an etch target film formed on the semiconductor substrate is etched. In this manner, a fine pattern that cannot be resolved by using a single layer resist can be formed in the etch target film.
The present inventors have carried out the etching method for an organic film of Conventional Example 5 by using an etching gas including an O2 gas under the following etching conditions:
Plasma etching system: NLD plasma etching system
Flow rate per minute in standard condition of etching gas:
O2=90 ml
Antenna power: 1000 W (13.56 MHz)
Bias power: 400 W (2 MHz)
Pressure: 0.133 Pa
Substrate cooling temperature: 0xc2x0 C.
Etching time: 4 minutes
FIGS. 23A and 23B are cross-sectional SEM photographs of holes formed in organic film patterns by the pattern formation method for Conventional Example 5, and the holes of FIGS. 23A and 23B have diameters of 0.18 xcexcm and 0.4 xcexcm, respectively. In FIGS. 23A and 23B, a reference numeral 271 denotes a silicon substrate, a reference numeral 272 denotes an organic film pattern, and a reference numeral 273 denotes a mask pattern of a silicon oxide film. The resist pattern formed on the mask pattern 273 is eliminated during formation of the organic film pattern by the dry development, and hence, the etch target film deposited on the silicon substrate 271 is etched by using a two-layer mask pattern consisting of the organic film pattern 272 and the mask pattern 273.
The etch shape (the cross-sectional shape of the hole) is apparently a good anisotropic shape (vertical shape) as is shown in FIGS. 16A through 16D.
It is, however, understood through detailed observation of FIGS. 16A through 16D that the hole actually has a bowing cross-section. A bowing cross-section means an arched overhang cross-section. As is obvious from FIGS. 16A through 16D, the hole formed in the organic film 102 through the etching has a larger diameter than the diameter of the opening of the mask pattern 103.
Accordingly, the etching method for Conventional Example 1 has a problem that a hole formed in the organic film 102 cannot have a cross-section tapered toward the bottom (hereinafter referred to as a forward taper cross-section).
In Conventional Example 2, when the organic film 215 is etched by the method for Conventional Example 1, the recess 218 is formed to have a bowing cross-section as is shown in FIG. 18A.
Since the cross-section of the recess 218 is in the bowing shape, when the third barrier metal layer 219 with a small thickness is formed on the wall of the recess 218, the third barrier metal layer 219 cannot be uniformly formed on the wall of the recess 218 as is shown in FIG. 18B. Specifically, the third barrier metal layer 219 is separated (disconnected) in a portion 220 just below the mask pattern 216A on the wall of the recess 218 and on a bottom 221 of the recess 218.
Accordingly, in forming the connection plug or the metal interconnect 223 by filling the recess 218 with the conducting film 222 by the CVD or plating, the conducting film 222 cannot be uniformly filled. Specifically, since the third barrier metal layer 219 is separated in the portion 220 just below the mask pattern 216A on the wall of the recess 218 and on the bottom 221 of the recess 218, the third barrier metal layer 219 is electrically insulated, namely, separated. Therefore, for example, when the conducting film 222 of copper is filled by electroplating, an electric potential cannot be applied to a portion of the third barrier metal layer 219 inside the recess 218, and hence, the conducting film 222 cannot be uniformly filled in the recess 218. Alternatively, when the recess 218 is filled with the conducting film 222 of tungsten, a tungsten film is abnormally grown in the separated portions of the third barrier metal layer 219, and hence, the conducting film 222 cannot be uniformly filled in the recess 218. Since the conducting film 222 cannot be uniformly filled in the recess 218 in this manner, the connection plug or metal interconnect 223 is defective. As a result, the electric characteristic is disadvantageously degraded so as to degrade the reliability of the semiconductor device.
In Conventional Example 3, when the second organic film 238 and the first organic film 235 are etched by the method for Conventional Example 1, the interconnect groove 241 and the via hole 242 are formed to have a bowing cross-section as is shown in FIG. 21B.
Furthermore, the deposition including the reaction product and silicon is adhered onto the wall of the via hole 242 as described above. In addition, while the second barrier metal layer 234 is over-etched, the first mask pattern 236A serving as an effective etching mask for forming the via hole 242 is etched through ion sputtering during the etching. Accordingly, the opening of the first mask pattern 236A is enlarged as is shown in FIG. 21C. Therefore, the bowing cross-section of the via hole 242 in the first organic film 235 becomes more serious, and since the wall of the via hole 242 is thus recessed, the barrier wall 243 in a crown shape is formed on the bottom of the via hole 242 from the deposition including the reaction product generated in the etching and silicon.
Accordingly, when the interconnect groove 241 and the via hole 242 are filled with the conducting film by the CVD or plating to form the connection plug and the metal interconnect, the conducting film cannot be uniformly filled, and a connection failure is caused between the connection plug filled in the via hole 242 and the lower metal interconnect. As a result, a multi-level interconnect structure is difficult to form by the dual damascene method.
In Conventional Example 4, when the organic film 252 is etched by the method for Conventional Example 1, the opening 259 of the organic film pattern 252A is formed to have a bowing cross-section as is shown in FIG. 22D. When the organic film pattern 252A having such a hole with the bowing cross-section is used for etching mask, it is difficult to conduct highly precise etching.
In Conventional Example 5, since the organic film is subjected to the dry development carried out by plasma etching using an etching gas including an O2 gas as a principal constituent, the hole formed in the organic film pattern 272 has a larger diameter than the opening of the mask pattern 273 and the hole formed in the organic film pattern 272 has a bowing cross-section as is shown in FIGS. 23A and 23B. When the organic film pattern 272 having such a hole with the bowing cross-section is used for etching the etch target film, it is difficult to conduct highly precise etching.
Therefore, in a method proposed for suppressing the hole of the organic film pattern 272 from having a bowing cross-section, the dry development is carried out on the organic film with the actual substrate temperature kept at a temperature below the freezing point by setting the substrate cooling temperature (refrigerant temperature) to 20xc2x0 C. through 50xc2x0 C. below zero.
In order to attain such a low temperature, however, excessive cost and a large-scaled system are required, and hence, there arise problems of increase of the system cost and decrease of the system stability.
Accordingly, it is impossible to form a hole with a forward taper cross-section in an organic film pattern by the method for Conventional Example 5.
Needless to say, the problems of Conventional Example 5 (the three-layer resist process) also arise in Conventional Example 4 (the top surface imaging process).
In consideration of the aforementioned conventional problems, a first object of the invention is forming a recess with a forward taper cross-section in an organic film by etching the organic film.
A second object of the invention is forming a recess with a forward taper cross-section in an organic film by plasma etching and uniformly forming a barrier metal layer on the wall of the recess, so that the recess can be uniformly filled with a conducting film.
Furthermore, a third object of the invention is forming an organic film pattern having an opening with a forward taper cross-section in dry development (plasma etching) of the organic film, so as to precisely conduct the etching with a large process margin.
The first method for etching an organic film of this invention comprises a step of etching an organic film by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a nitrogen component.
In the first method for etching an organic film, since the etching gas includes the compound including carbon, hydrogen and nitrogen, the plasma generated from the etching gas includes radicals of CHx (wherein x is 1, 2 or 3) that can easily form a polymer on an etch target surface. The polymer of the CHx radicals adhered onto the wall of a recess formed in the organic film works as a sidewall protection film for preventing an ion assisted reaction, and hence, the recess can be formed to have a forward taper cross-section. Furthermore, since the nitrogen component for supplying N ions to the plasma is included in the etching gas, a substantially constant etching rate can be kept, and the angle of the forward taper cross-section of the recess can be controlled by adjusting the mixing ratio of the nitrogen component.
Accordingly, in the first method for etching an organic film, a recess with a forward taper cross-section can be formed in an organic film, and the angle of the forward taper cross-section can be controlled while keeping a substantially constant etching rate.
In the first method for etching an organic film, the second gas is preferably a nitrogen gas.
In this manner, N ions and N2 ions can be supplied to the plasma, and hence, the angle of the forward taper cross-section of the recess can be easily controlled.
In the first method for etching an organic film, the second gas is preferably a mixed gas including a nitrogen gas and a hydrogen gas.
In this manner, while keeping controllability of the angle of the forward taper cross-section of the recess, the etching rate can be improved.
In the first method for etching an organic film, the second gas is preferably an ammonia gas.
In this manner, the controllability of the angle of the forward taper cross-section of the recess and the improvement of the etching rate can be both realized.
In the first method for etching an organic film, the second gas preferably further includes a rare gas.
In this manner, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state. Furthermore, the recess can be more definitely formed in a forward taper cross-section.
The second method for etching an organic film of this invention comprises a step of etching an organic film by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a rare gas.
In the second method for etching an organic film, since the etching gas includes the compound including carbon, hydrogen and nitrogen as well as the rare gas, a recess having a forward taper cross-section can be definitely formed in the organic film. Furthermore, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state for a long period of time.
Accordingly, in the second method for etching an organic film, a recess can be definitely formed in an organic film to have a forward taper cross-section, and a deposition film formed on inner walls of a reaction chamber can be reduced so as to keep the reaction chamber in a stable state.
The third method for etching an organic film of this invention comprises a step of etching an organic film by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including an oxygen component.
In the third method for etching an organic film, since the etching gas includes the compound including carbon, hydrogen and nitrogen, a recess formed in the organic film can attain a forward taper cross-section. Furthermore, since the etching gas includes the oxygen component, the etching rate can be improved.
Accordingly, in the third method for etching an organic film, while improving the etching rate, a recess with a forward taper cross-section can be formed in an organic film.
In the third method for etching an organic film, the second gas preferably further includes a rare gas.
In this manner, the recess formed in the organic film can more definitely attain the forward taper cross-section, and a deposition film formed on inner walls of a reaction chamber can be reduced so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state.
The first method for fabricating a semiconductor device of this invention comprises the steps of forming an organic film on a semiconductor substrate; forming, on the organic film, a mask pattern including an inorganic compound as a principal constituent; and forming a recess in the organic film by selectively etching the organic film by using the mask pattern and by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a nitrogen component.
In the first method for fabricating a semiconductor device, a recess is formed in an organic film by the first method for etching an organic film, and hence, the recess can be formed in the organic film in a section not in a bowing shape but in a forward tapered shape. Therefore, a barrier layer can be uniformly formed on the wall of the recess without having a separated portion, and hence, the recess can be definitely filled with a conducting film. Accordingly, a connection plug or a buried interconnect with a good electric characteristic can be formed. Furthermore, since the etching gas includes the nitrogen component for supplying N ions to the plasma, the angle of the forward taper cross-section of the recess can be controlled by adjusting the mixing ratio of the nitrogen component.
Accordingly, in the first method for fabricating a semiconductor device, since a recess can be definitely filled with a conducting film, a connection plug or a buried interconnect with a good electric characteristic can be formed, and the angle of the forward taper cross-section of the recess can be controlled.
In the first method for fabricating a semiconductor device, the second gas is preferably a nitrogen gas.
In this manner since N ions and N2 ions can be supplied to the plasma, the angle of the forward taper cross-section of the recess can be easily controlled.
In the first method for fabricating a semiconductor device, the second gas is preferably a mixed gas including a nitrogen gas and a hydrogen gas.
In this manner, while keeping the controllability of the angle of the forward taper cross-section of the recess, the etching rate can be improved.
In the first method for fabricating a semiconductor device, the second gas is preferably an ammonia gas.
In this manner, the controllability of the angle of the forward taper cross-section of the recess and the improvement of the etching rate can be both realized.
In the first method for fabricating a semiconductor device, the second gas preferably further includes a rare gas.
In this manner, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state for a long period of time. Furthermore, the recess can more definitely attain the forward taper cross-section, resulting in forming a connection plug or a buried interconnect with a better electric characteristic.
The second method for fabricating a semiconductor device of this invention comprises the steps of forming an organic film on a semiconductor substrate; forming, on the organic film, a mask pattern including an inorganic compound as a principal constituent; and forming a recess in the organic film by selectively etching the organic film by using the mask pattern and by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a rare gas.
In the second method for fabricating a semiconductor device, since a recess is formed in an organic film by the second method for etching an organic film, the recess with a forward taper cross-section can be formed in the organic film. Therefore, a barrier layer can be uniformly formed on the wall of the recess without having a separated portion. Accordingly, the recess can be definitely filled with a conducting film, and hence, a connection plug or a buried interconnect with a good electric characteristic can be formed. Furthermore, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state.
Accordingly, in the second method for fabricating a semiconductor device, since a recess can be definitely filled with a conducting film, a connection plug or a buried interconnect with a good electric characteristic can be formed, and a deposition formed on inner walls of a reaction chamber can be reduced so as to keep the reaction chamber in a stable state.
The third method for fabricating a semiconductor device of this invention comprises the steps of forming an organic film on a semiconductor substrate; forming, on the organic film, a mask pattern including an inorganic compound as a principal constituent; and forming a recess in the organic film by selectively etching the organic film by using the mask pattern and by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including an oxygen component.
In the third method for fabricating a semiconductor device, since a recess is formed in an organic film by the third method for etching an organic film, a recess with a forward taper cross-section can be formed in the organic film. Therefore, a barrier layer can be uniformly formed on the wall of the recess without having a separated portion. Accordingly, the recess can be definitely filled with a conducting film, and hence, a connection plug or a buried interconnect with a good electric characteristic can be formed. Furthermore, since the etching gas includes the oxygen component, the etching rate can be improved.
Accordingly, in the third method for fabricating a semiconductor device, since a recess can be definitely filled with a conducting film, a connection plug or a buried interconnect with a good electric characteristic can be formed, and the etching rate can be improved.
In the third method for fabricating a semiconductor device, the second gas preferably further includes a rare gas.
In this manner, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state. Furthermore, the recess can definitely attain a forward taper cross-section, so as to form a connection plug or a buried interconnect with a better electric characteristic.
In any of the first through third methods of fabricating a semiconductor device, the recess preferably includes a via hole and an interconnect groove formed above the via hole and is filled with a conducting film by a dual damascene method.
In this manner, not only a barrier layer can be uniformly formed on the walls of the via hole and the interconnect groove without having a separated portion (disconnected portion) but also a crown-shaped barrier wall can be prevented from being formed on the bottom of the via hole. Therefore, the via hole and the interconnect groove can be definitely filled with the conducting film. Accordingly, the electric characteristics of a connection plug filled in the via hole and a metal interconnect filled in the interconnect groove can be improved, and a connection failure between the connection plug and a lower metal interconnect can be avoided. As a result, a multi-level interconnect structure with a good electric characteristic can be formed by the dual damascene method.
The first pattern formation method for this invention comprises the steps of forming an organic film on a substrate; forming, on the organic film, a mask layer including an inorganic component; and forming an organic film pattern from the organic film by selectively etching the organic film by using the mask layer and by using plasma generated from an etching gas including a first gas containing, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a nitrogen component.
In the first pattern formation method, an opening is formed in the organic film by the first method for etching an organic film. Therefore, while keeping a substantially constant etching rate, an opening with a forward taper cross-section can be formed in the organic film. Specifically, the opening of the organic film pattern never has a cross-section in a bowing shape, and hence, an etch target film can be precisely etched with a large process margin.
Accordingly, in the first pattern formation method, since an opening with a forward taper cross-section can be formed in an organic film, an etch target film can be precisely etched with a large process margin, and an organic film pattern can be formed in a substantially constant etching rate.
In the first pattern formation method, the second gas is preferably a nitrogen gas.
In this manner, since N ions and N2 ions can be supplied to the plasma, the angle of the forward taper cross-section of the opening formed in the organic film can be easily controlled.
In the first pattern formation method, the second gas is preferably a mixed gas including a nitrogen gas and a hydrogen gas.
In this manner, while keeping the controllability of the angle of the forward taper cross-section of the opening, the etching rate can be improved.
In the first pattern formation method, the second gas is preferably an ammonia gas.
In this manner, the controllability of the angle of the forward taper cross-section of the opening and the improvement of the etching rate can be both realized.
In the first pattern formation method, the second gas preferably further includes a rare gas.
In this manner, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state. Furthermore, the opening formed in the organic film can more definitely attain a forward taper cross-section, so as to etch an etch target film more precisely with a larger process margin.
The second pattern formation method for this invention comprises the steps of forming an organic film on a substrate; forming, on the organic film, a mask layer including an inorganic component; and forming an organic film pattern from the organic film by selectively etching the organic film by using the mask layer and by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including a rare gas.
In the second pattern formation method, since an opening is formed in the organic film by the second method for etching an organic film, an opening with a forward taper cross-section can be formed in the organic film, and hence, the opening of an organic film pattern can be prevented from having a cross-section in a bowing shape. Accordingly, an etch target film can be precisely etched with a large process margin. Furthermore, since a deposition film formed on inner walls of a reaction chamber can be reduced, the frequency of cleaning the reaction chamber can be reduced, so as to keep the reaction chamber in a stable state.
Accordingly, in the second pattern formation method, since an opening with a forward taper cross-section can be formed in an organic film, an etch target film can be precisely etched with a large process margin, and a deposition film formed on inner walls of a reaction chamber can be reduced so as to keep the reaction chamber in a stable state.
The third pattern formation method for this invention comprises the steps of forming an organic film on a substrate; forming, on the organic film, a mask layer including an inorganic component; and forming an organic film pattern from the organic film by selectively etching the organic film by using the mask layer and by using plasma generated from an etching gas containing a first gas including, as a principal constituent, a compound including carbon, hydrogen and nitrogen and a second gas including an oxygen component.
In the third pattern formation method, an opening is formed in the organic film by the third method for etching an organic film. Therefore, an opening with a forward taper cross-section can be formed in the organic film, and the opening of an organic film pattern can be prevented from having a cross-section in a bowing shape. Accordingly, an etch target film can be precisely etched with a large process margin. Furthermore, since the etching gas includes the oxygen component, the etching rate in forming the organic film pattern can be improved.
Accordingly, in the third pattern formation method, since an opening with a forward taper cross-section can be formed in an organic film, an etch target film can be precisely etched with a large process margin, and the etching rate in forming an organic film pattern can be improved.
In the third pattern formation method, the second gas preferably further includes a rare gas.
In this manner, a deposition film formed on inner walls of a reaction chamber can be reduced, so as to reduce the frequency of cleaning the reaction chamber. Therefore, the reaction chamber can be kept in a stable state. Furthermore, an opening formed in an organic film can more definitely attain a forward taper cross-section, so as to etch an etch target film more precisely with a larger process margin.
In any of the first through third pattern formation methods, the mask layer is preferably a silylated layer.
In this manner, an opening with a forward taper cross-section can be formed in an organic film pattern by a top surface imaging process.